Split phase impulser for musical instruments



Patented Feb. 11, 1936 UNITED STATES SPLIT PHASE IMPULSER FOR MUSICAL INSTRUMENTS Victor H. Severy, Los Angeles, Calif., alsignor, by mesne assignments, to Creative Industries, 1110., a corporation of Nevada Application July 19, 1933, Serial No. 681,108

13 clai s.

the same and connected up into a circuit so that the magnet is energized at a frequency corresponding to the natural rate of vibration of the string. However, such magnets have been placed on one side only of the string, and the resiliency oi the string has been relied upon to return the string after it has been deflected by the attraction of the magnet.

The general object of this invention is to provide simple means for developing magnetic attraction on both sides of a vibrator, for example,

a piano string, and to provide simple means whereby the magnets on opposite sides of the string are alternately energized to produce an alternating attraction to the string. In other words, magnetization of the upper'magnet operates to pull the string upwardly, and this attraction is immediately followed by a pull exerted by the lower magnet. These pulls alternate at a frequency corresponding to the vibratory rate of the string, and the result is that when the control circuit is closed, the string very quickly reaches its full amplitude of vibration.

A further object of the invention is to provide simple means for cooperating with electro-magnetic apparatus of this kind, which will enable the desired efi'ects to be attained through the use of a pulsating or alternating current in which the pulsations or alternations recur at a definite frequency, preferably the same as the natural period of vibration of the string.

In practice, the apparatus involves the use of magnetic poles with exciting coils for the same, which develop poles of a definite correlated character. Associated with these poles, I provide oscillating coils which pass current to produce definite correlated magnetizing effects on these poles in such a way that for one direction of impulse or phase, the magnetization of the poles on one side of the vibrator will be neutralized, while the magnetization on the other side will be intensifled. In this way, attraction for the string is developed pulling first in one direction and then in the other, and alternating at the frequency for .the note corresponding to that string. One

5 of the objects of the invention is to provide simple means for simultaneously varying the resistances in the exciting circuit, and in the oscillating circuit, so as to maintain a substantial balance in the magnetizing efl'ects of the current flowing in the two circuits.

Further objects of the invention will appear hereinafter.

The invention consists in the novel parts and combination of parts to be described hereinafter, all of which contribute to produce an efllcient split phase impulser for musical instruments.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims.

In the drawing:

Figure 1 is a diagrammatic view illustrating a preferred embodiment of the apparatus;

Figure 2 is a diagrammatic view indicating the manner in which the vibrator or string is made to vibrate by the electromagnets; and

Figure 3 is a diagram illustrating the character of the magnetic pull exerted upon the string.

Before proceeding to a more detailed description of the invention, it should be stated that it involves the principle of providing two magnetic poles, one being located on one side of the vibrator or string, and the other on the other side. These poles are preferably located opposite to each other and have a definite correlated character. The poles are preferably developed through the agency of exciting coils which are in an exciting circuit carrying a direct current. According to my invention, 1 provide oscillating coils associated respectively with their corresponding poles, and through these coils I pass a pulsating or alternating current in a direction and at a frequency which will enable the same to cooperate with the poles to increase the magnetization of one of the poles on one side of the vibrator, while simultaneously reducing and neutralizing the magnetization of the opposite pole. In this the string byelectromagnetic means, and dis-- penses with the necessity for employing the regular hammer action of the piano. The abmlute character or signs of the poles of the magnets are unimportant, so long as these have a definite correlated relation. In the present instance, the direction of flow of the current in the exciting coils is such as to produce two opposed north poles and two opposed south poles. The direction of fiow in the oscillating coils corresponding to, the different poles, is such that when the fiow or. phase is in one direction, the magnetization of the poles on one side of the string will be neutralized or reduced, while the magnetization of the poles on the other side will be increased. In this way, at

each alternation of the current or phase, the

direction of attraction on the string will be reversed. The invention is preferably practiced by providing a bipolar magnet on each side of the string, and providing an exciting coil around the shank of the magnet between its poles. The magnet is preferably of horseshoe form, and the exciting coils are excited by a'direct current. In order to balance the relation of the magnetizing eil'ects of the alternating current and the current in the exciting circuit, I prefer to provide for simultaneously varying the resistances in these circuits. In other words, in accordance with my invention, I provide magnetic means having a pole located on one side of the vibrator, and having a pole located on the other side of the vibrator, with an oscillating coil corresponding to each pole, and with this I employ means for passing a pulsating or alternating current of definite frequency through the coils in a direction to energize the poles alternately.

Referring more particularly to the parts, and especially to Figure 1, I indicates a} support for a vibrator, which, in the present instance, is the sounding-board of a piano on which the vibrator in the form of a string 2 is mounted, and stretched between the bridges 3. In applying my invention to such a stringed instrument, I provide electromagnetic means preferably including two bipolar magnets M and M, one of which is located above the string and the other below the string. These magnets are of horseshoe form, and the shank of each magnet is provided with an exciting coil 4. These coils are wired in any suitable manner, into an electric circuit 5 for exciting the coils, said circuit including a source of electromotive force such as a battery 8. In the present instance, the coils are wired in series.

The passing of the current through the coils in the direction indicated in the vertical arrow Figure 1, will result in producing two north poles N and N, and two south Poles 8 and 8. These poles will be located opposite to each other as indicated, that is to say, the two north poles are opposite to each other and the two south poles are opposite to each other. Each pole is provided with a corresponding oscillating coil I, and these coils are wrapped around their corresponding poles in such a way that when a current names in a certain direction, it will have a magnetic efiect on the poles which will neutralize the magnetism developed by the corresponding exciting coil as regards one of the bipolar magnets, and will increase the magnetization of the poles on the opposite bipolar magnet. This efi'ect will be attained with oscillating windings as illustrated in Figure 1. For example, assuming that the bipolar magnets have their north poles opposite to each other, and assuming that the current for the oscillating coils fiows in the direction of the solid line arrow 80 on circuit wire 3, then the effect of thefiow inthe coils Iwillbe asregards themaga,oso,aso

net M to produce magnetization of a south character at the pole N, and magnetization of a north character at the pole S. In other words, the positive character magnetization at the pole marked N will be neutralized, and so will the magnetization of a negative sign at the pole S.

While the efiect of this magnet M is being neutralized, the coil I on the other side of the string will have the effect of increasing the magnetization at the pole N and at the pole S. If, on the other hand, the current in the wire 8 flowed in the opposite direction as indicated by the dotted arrow, opposite effects would be induced in the magnets, and the magnetization of the poles N and 8 would be increased or intensified, while the magnetization of the poles N and S would be reduced or neutralized. By having the frequency of alternation the same as the natural period of vibration of the string, it can immediately be brought to its full amplitude of vibration.

Any suitable means may be employed for producing alternations at frequency corresponding to the difierent strings. In Figure l I illustrate means for accomplishing this, which includes an induction generator having a rotor I carrying 'a plurality of insualted metallic armatures I I. The rotor III is rotated at a high speed, which can be controlled so that the armatures I I pass poles I2 located circumferentially on a stator I3. Opposite the poles I2 a second set of poles It are provided, which are also mounted fixed in the stator I3, and which are excited by coils I5 connected into an exciting circuit I6 including a source of electromotive force such as a battery II. This circuit may include a hand-controlled switch I3. The rotor I0 should be rotated at the proper speed to enable the armatures II to pass the poles I2 at a frequency corresponding to the period of vibration of the string 2. The rotor III may be driven by any suitable means, for example, by means of a belt passing over a belt pulley 2|.

The coils 22 of the poles I2 are connected into a circuit 23 that includes the wire 8 already referred to, and this circuit also includes a conductor or wire 24 connected with the other side of the coils I. The circuit 23 also includes normally open contacts 25 and 26, the former of which is fixed, and the latter of which is carried on the end of the piano key 21 corresponding to this string.

The efiect of the alternating current will be to vibrate the string as indicated diagrammatically at A and A in Figure 2. The eifect of the pull of the upper magnet and the lower magnet on the string, is illustrated in Figure 3. At the points A the upper magnet M exerts a maximum pull upon the string. At the points A the magnet M' exerts its maximum pull, and at the point where the reversal of alternation occurs, no pull on the string in either direction is occurring, and these points are indicated by the numeral 28.

It is necessary to provide for balancing the exciting effects of the exciting coils I and the oscillating coils I. For this purpose I prefer to provide two variable resistances 29; and 33, the former of which is connected into the circuit 23, and the latter of which is connected into the exciting circuit 5. The movable arms 3| and 32 of the resistances or rheostats are connected up in some way to enable them to be operated simultaneoualy, so that if the resistance in the oscillating circuit is varied, a corresponding variation in the resistances in the exciting circuit will occur. Any suitable means may be employed for operating the arms 3| and 32 simultaneously. In the pole located on the other side of the vibrator, an

present instance, this is accomplished y Providing a push rod 88 having a pin-and-slot connection with each arm and guided to slide in suitable fixed supports 35. The end of this adlusting rod may be actuated by a bell crank lever 31 controlled by a flexible wire 31 in a sheath ll,

connected to a pedal 3! within convenient reach of the player's foot.

One of the advantages arising from the practice of this invention, is that even if the strings of the piano are "out of tune" they'will be vibrated at their proper frequency by the magnets.

It also frequently happens that in the cheaper types of pianos the strings tend to vibrate in such a way that undesirable partials occur during the vibration of the strings. In such a case, by placing the magnets at certain points on each string the string can be induced to vibrate with definite desired partials that dominate, and suppress the undesired partials.

- It is understood that the' embodiment of the invention described herein, is only one of the many embodiments this invention may take, and

I do not wish to be limited in the practice of the' invention, nor in the claims, to the particular embodiment set forth.

I claim:

i. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator and having a pole located on the other side of the vibrator, a

: coil corresponding to each pole, and means for passing a sine-wave pulsating current of definite frequency through said coils in a direction to energize said poles alternately.

2. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator and having a pole located on the other side of the vibrator, an oscillating coil corresponding to each pole, and means for passing an alternating current through said coils, operating to produce attraction for the vibrator alternating from one pole to the other.

3. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator and having a pole located on the other side of the vibrator, an oscillating coil corresponding to each pole, an electric circuit passing through said coils, and means for generating an alternating current in said circuit, operating to produce attraction for the vibrator alternating from one pole to the other.

4. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator and having a pore located on the other side of the vibrator, an oscillating coil corresponding to each pole, 'means connecting said coils, and means for passing a sine-wave current through the coils in a direction that will increase the magnetization of one of the poles and simultaneously reduce the magnetization of the other pole.

5. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator and having a pole located on the other side of the vibrator, an oscillating coil corresponding to each pole, means connecting said coils, and means for passing a sine-wave pulsating current of definite frequency through said coils, and in a direction to increase the magnetization of said poles alternately.

6. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator and having a oscillating coil corresponding to each pole, means connecting said coils, and means for passing an alternating current through said coils at a frequency corresponding to the natural period of vibration of the vibrator.

7. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole of a definite character located on one side of the vibrator and having a pole of a definite character located on the other side of the vibrator, a coil corresponding-to each pole, means for passing an alternating current through said coils, and means for connecting the coils so that the current will pass in a direction to increase the magnetization of one of the poles and simultaneously reduce the magnetization of the opposite pole.

8. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator with an exciting coil, and having a pole located on the other side of the vibrator with an exciting coil, means for passing current through said coils, an oscillating coil corresponding to the first pole and an oscillating coil corresponding to the other pole, said two exciting coils operating to give said poles a definite correlated character, and means for passing an alternating current through the two oscillating coils and operating to reduce the magnetization of one pole and simultaneously increase the magnetization of the other pole so that the magnetic pull exerted by one pole is immediately followed by a magnetic pull exerted by the opposite pole.

9. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole with an exciting coil, located on one side of the vibrator and having a'pole with an exciting coil located on the other side of the vibrator, means for passing a current through said exciting coils so as to develop a magnetization of a definite character in the first-named pole and magnetization of a definite correlated character in the opposite pole, an oscillating coil corresponding to the firstnamed pole, and an oscillating coil corresponding to the second-named coil, means connecting said oscillating coils, and means for passing an alternating current of definite frequency through the said oscillating coils, said oscillating coils operating to pass the current aroimd the poles in a direction to reduce the magnetization oi one pole while increasing the magnetization of the opposite pole.

10. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator with an exciting coil and having a pole located on the other side of the vibrator with an exciting coil, a circuit passing through said exciting coils, an oscillating coil corresponding to the first pole, and an oscillating coil corresponding to the other pole, said two exciting coils operating to give said poles a definite character, a circuit passing through the oscillating coils, means in said last-named circuit for passing an alternating current through the two oscillating coils and operating to reduce the magnetization of one pole and simultaneously increase the magnetization of the other pole, resistances located respectively in said circuits, and means for simultaneously varying said resistances.

11. In apparatus foroscillating a vibrator, the combination of magnetic means having a bipolar electromagnet located with its poles on one side of the vibrator and having a bipolar magnet with its current through the oscillating coils in a direction to cooperate with-the poles so as to increase the magnetization of the poles of one bipolar magnet while simultaneously neutralizing the magnetism tion of the poles oi the opposite bipolar magnet.

12. In apparatus for oscillating a vibrator, the combination of magnetic means having a pole located on one side of the vibrator and having a pole located on the other side oi the vibrator, an oscillating coil corresponding to each pole, means for generating a sine-wave alternating current and for passing the same through said coils, said oscillating coils operating to develop an attraction for the vibrator alternating from one pole to the other.

13. In apparatus for oscillating a vibrator, the combination oi magnetic means having a pole with an exciting coil, located on one side of the vibrator and having a pole with an exciting coil located on the other side of the vibrator, means for passing a current through said exciting coils so as to develop a magnetization oi a definite character in the first-named pole and magnetization a! a definite correlated character in the opposite pole, an oscillating coil corresponding to the first-named pole, an oscillating coil correcoils operating to pass the current around the" poles alternately in a direction to reduce magnetization oi one pole while increasing the magnetization of the opposite pole.

VICTOR H. SEVERY.

sponding to the second-named coil, means con- 

